For many years, nobody knew what giant squid ate. But recent studies have shown that giant squid eat deep-sea fishes, such as orange ruffie, and hokie. They also eat squids, deep-sea squids, other kinds of squid, not architeuthis, not the giant squid.
The other way I like to answer this question is that they eat anything they want to. Because when they are adults, they are very large. They would be able to capture almost anything that struck their fancy.
